This package provides users with the ability to query the Human Cell Atlas data repository for single-cell experiment data. The projects(), files(), samples() and bundles() functions retrieve summary information on each of these indexes; corresponding *_details() are available for individual entries of each index. File-based resources can be downloaded using files_download(). Advanced use of the package allows the user to page through large result sets, and to flexibly query the 'list-of-lists' structure representing query responses.